No offence to your opinion but my thinking is the direct opposite. If you ever have a spouse who cheated, all the more need a spyware. Precisely they already proven that their words are not trustworthy (that's why we don't trust them. And since they ready cheated, proven that our judgement is wrong in the first place) that's why the wayward spouse need to install the app to verify that this time round, the cheated spouse wants to do exactly what they say they will do. Their words tally with their actions now. Probably verifying for a certain period of time and finally the trust is back then the wayward spouse can trust the cheated spouse back without using a spyware. I think the spyware is also another way for the wayward spouse to find a way to trust back their repentant spouse. At least I think it works better for me. I trust totally the first time round without spyware but if he cheated, I can't just trust without anything to help me the second time round. So a spyware will let me know for certain he is where he claims he is and he is not lying anymore. That's how I can revive my marriage.If you ever had a partner/spouse cheated on you before and you want to forgive them and start anew, I would think it's best not to resort to adding a spyware on their phone. This shows that you do not trust them nor trust yourself in your own judgement. It will only bring you further worries. You will constantly think and think and overthink every little thing. It takes time to learn to let go but once you let go you will feel much more light-weighted on your shoulders.
On the other hand, it is not healthy for someone to use spyware if their spouse hasn't been caught cheating or lying.